Ewinor mcgrueb



E. McGRUER.

HOLLOW SPAR, WOODEN TUBE, AND THE LIKE.

APPLICATION FILED MAR. 26. I918.

Patented'Aug. 26,1919.

EWING MOGRUER, 0F LAMBETH, LONDON, ENGLAND.

HOLLOW SPAR, woonrnv TUBE, AND THE LIKE,

A Application filed March 26. 1918. Serial No. 224,861.

T 0 all whom it may concern:

Be it known that I, EWING MoGnunR, a

subject of the King of Great Britain, 'residing at Commercial Wharf,Lambeth, London, England, have invented a new and useful Improvement inHollow Spars, lVooden Tubes, and the like, of which the following is aspecification.

This invention relates to improvements in hollow spars, tubes and likearticles of wood, and is especially applicable to bentwood hollow sparsas described in the specification of my U. S. Patent No, 1,266,696 ofMay 21, 1918.

According to the invention shown and described in said patent a board isquartersawed in the direction of the grain and wetted on one side andheated on the other so that the fibers stretch and contract transverselyin any ratio up to 40 of their original breadth and so allow the boardto be bent on the neutral axis of its transverse section. As describedin said patent, a hollow body is constructed consisting of twoquarter-sawed boards bent into form and provided with lap joints, theedges of the boards being glued or cemented together at the joints. Insuch construction the end grain or natural annual grain rings of oneboard lie toward the opposite hand to that of the other board. Inconstructing the hollow bodies the boards before being bent are wcttedon one side and heated on the other. One method is to place a board on asteam heated mandrel of the shape required and at the same time to applywater to the other side of the board. In this manner the fibers arecontracted on the heated side and stretched on the Wetted side.

One object of this invention is to dispense with the use of formers orcores in the manufacture of tapered hollow spars either straight orcurved.

According to this invention, the two edges of a board bent around toform a spar or tube are inserted into grooves formed on opposite sidesof a strip of wood, the edges being secured in the grooves by glue orthe like. If desired the outer projecting pOI'tiOn of the strip may beplaned ofl', more especially in the case in which the spar or tubeconsists of two or more laminae. I

In the manufacture of spars or tubes of large diameter two or moregrooved strips are employed and distance pieces are hi Specification ofLetters Patent.

Patented Aug. 6, 1919.

sorted between them and secured to the strips. 7

' "In'the accompanying drawings, Figure 1 is a cross section of agrooved strip, the angle between the grooves being determined by thecurvature in cross section of the spar to he made; Fig. 2 is a crosssection of a hollow spar made with two laminae; Fig. 3 is a crosssection of a hollow spar made with two laminae and two grooved strips inwhich a block is fitted; Fig. 4 is a longitudinal section of acurved-tapered spar having blocks fitted to both ends; Fig. 5 is a crosssection of the same at the ends of the layers; and Fig. 6 shows a hollowspar fitted to metal work, such as a gaff-jaw.

lVhen a hollow spar is made of one lamina, a board is bent around andits edges are inserted into the grooves a of a strip Z), as shown inFig. 1. When it is made of two or more laminae, the inner lamina isfirst made in likemanner to the hollow spar of one lamina. Referring toFigs. 2 and 3, c is the inner lamina secured to the strip 6, and asecond lamina (Z is bent around the first which forms a core. The edgesof the second lamina (Z are then glued together. Other laminae may besimilarly secured around the second.

In Fig. 3, two strips 6 are employed and a distance piece is used, theends of which are shaped to receive the strips Z). Such distance piecesare placed at a distance of two or three feet apart within the hollowspar.

Referring to Figs. I and 5, the spar consists of two laminae g and h anda grooved strip 7' to whose ends are secured blocks 70 by which the endsof the hollow spar are closed.

In Fig, 6, the spar consists of two laminae Z and m, two strips n and 0,and a block 7) which acts as a distance piece. q is a metal fittingwhich is secured to the hollow spar by means of bolts 1- which passthrough the block 79.

A hollow spar may conveniently be made by securing a strip at its endsto two blocks which may be secured to arms projecting from the workbench. The edges of a lamina, to which glue has been applied, areinserted into the grooves in the strip, an secured there by straps untilthe glue is dry.

lVhat I claim is: v

1. The process herein described of forming a hollow body which consistsin bending a quarter-sawed. board, to form said hollow body,.seonringgfhe-iends of said board to an interpose'cl wooden strip whichpro ects within and also extends outside of said body,

removing the outwardly projecting portion of said strip and then bending:a similar board around the hollow body and securing its ends to eachother. i

. 2." The process herewith-described of forming a hollow body, whichconsists-in bend 1Q ing a board to form said hollow body, se-

G'o'pies'of this patent may be obtained for .ouring the ends of saidboard to, 5011 interposed grooved wooden strip which projects within andalso outside of said body and then removing" the outwardly projecting EI GMOGRUER.

